What is the diameter of the acetylene light mirrors ?
Generally 5 1/2 to 6”
They are not all the same. You failed to mention the brand.
The convention in sizing Mangin mirrors was to use whole inches. Model T used 6". Maybe Ken Parker will speak up; he's pretty knowledgeable about the lamps.
5 1/2" is a common size for smaller cars and on trucks. That is the maximum outside diameter of the glass. The focal length also varies between brands.
The Mangin mirrors were "measured" by the maximum diameter of the mirrored back surface. That is about 1/2" larger than the diameter across the "ground" lead edge of the 5 and 6 inch Mangin mirrors I have.
Here is a "6-inch" Lancaster Mangin that fits Model T gas headlamps
It is about 5-1/2" across the front edge.
The mirrors may very well have different focal lengths but it must not be very much. I set the burner/stand center line just about 1" in front of the "ground" edge of the Mangin and focus the lamp on my garage door.
Check your burners carefully on a test stand to be sure they light correctly before mounting near a mirror. You don't want an errant flame to crack a mirror!
Ken in Texas
I thought Lancaster Glass Corp. went out of business or just quit making mangin mirrors a few years back? They were the only manufacturers that I knew of...at least of the thick glass mirror most lights use. Our 1910 Buick Corcoran lights had a thin glass reflector. It was held in by a sheet metal ring. I used a curved glass off of a clock and had it silvered. It is very close to the original.
Doesn't E&J use a smaller diameter mirror than a Brown and Victor?
Here's a source I ran across recently:
E&J used 5" mirrors on some of their lamps but 6" on the Model T lamps.
The third number in the Edmunds & Jones model number denotes the mirror size. E&J search lights add a "0" to the model number but the third number is still the mirror size. Here is a 1910 add out of a trade magazine and you see the model/mirror size.
I don't know for sure, but I believe that a E&J-466 is a "branded" lamp with the "4" indicating Ford. Essentially, the same E&J-366 lamp that is available to the trade.
Does anyone have a "E&J-466" with another automobile manufacturer logo?
I also believe Greg is correct that the Mangins were in one inch increments but again have very little to go on except this additional add
As far as I can tell, Lancaster made the mirrors for years but no longer.
Verne is correct that a thin plate parabolic mirror was used. I have several Victor 6" lamps with this type mirror. Thin plate mirror on the left, thick Lancaster Mangin on the right.
The Corcoran brothers owned both Victor and Corcoran Lamp Companies.
The Mangin is a more precision mirror.
Ken in Texas
There are many differences between the E&J 366 and the 466.
The 366 has a smaller jamb, uses the same 8 inch door as the 666 and 656. There is a flat milled on top of the mounting lugs as well.
The original E&J 366 and 466 lamps I have had experience with had MacBeth Mangin mirrors.